1/2 Gallon is too small for a betta to be happy in.

I got my old betta a tank from Petsmart for about $12. I can't find it on their website, but I'll look harder later. You could also use a Keep-a-Critter (or whatever those things are called). It is basically a plastic carrying case that people use for small animals and the lid has vents in it. I know many people use it for bettas since they don't require a filter. They are pretty cheap, about $5 I think.